In an engine of a motorcycle, an outboard motor, or a vehicle, there are known engines in which cylinders are serially arranged, in which cylinders are arranged so as to face each other, in which each cylinder bank is arranged in a V-letter shape, and the like.
The V-type engine is typically constructed by installing first and second cylinder heads onto first and second cylinder banks of the cylinder block. First and second cylinder head covers are attached to the first and second cylinder heads. A crankshaft which extends in the longitudinal direction of the engine is rotatably provided at a central portion of the cylinder block. Auxiliary apparatuses such as a cam shaft of a valve gear system, a water pump, and the like are driven by the crankshaft.
Such a water pump is disclosed in JP-U-4-79932. According to the water pump disclosed in this publication, an impeller is fixed to one end of a pump shaft which is pivotally attached to a pump housing through a bearing, a sealing device is provided between the impeller and the bearing, upper and lower side drain passages communicate a hollow chamber between the bearing and the sealing device with the outside of the pump housing, a dust cover faces an opening on the hollow chamber side of at least the upper side drain passage, and a concave portion is formed in the dust cover.
With this conventional water pump, as shown in FIG. 10, the water pump 154 is attached to a cylinder block 104 of a V-type engine 102. A timing chain (not shown) is interposed through a timing chain cover 152 around a casing 158 of the water pump 154. The timing chain cover 152 is arranged around the casing 158 through a seal member 160 comprising an O ring. A timing chain line exists between the timing chain cover 152 and the cylinder-block 104. A lubricating oil passage (not shown) is formed and lubricating oil flows in the lubricating oil passage.
The casing 158 has a hub or housing portion 168 for a water pump bearing 170, and the portions near water drain hole portions 174-1 and 174-2 are directly bleached to the lubricating oil. Thus, when the water drain hole portions 174-1 and 174-2 are thermally influenced by the lubricating oil and are set to high temperatures and cooling water leaks from mechanical seal 166, a component in, for example, an LLC (Long Life Coolant) which is used as a cooling water is precipitated by the high temperature and is deposited and chokes the water drain hole portions. The cooling water may then enter the water pump bearing so that the life of the bearing is reduced, and this is practically disadvantageous.
As also shown in FIG. 10, the water pump bearing 170 is inserted with pressure (i.e. a press fit) into the housing portion 168 of the casing 158. In the case where the coefficient of thermal expansion of the material of the casing 158 is larger than that of the material forming the outer race 184 of the bearing 170, when the heat of the lubricating oil acts on the housing portion 168 of the casing 158, the inner diameter of the housing portion 168 increases, and a magnitude of the pressure fit of the bearing 170 within the housing decreases, so that there is an inconvenience in that the bearing 170 may drop out. There are also inconveniences in that a holder 188, the lip seal 172, grease, etc., as component parts of the water pump bearing 170 itself, are also deteriorated by the heat. The life of the bearing is thus reduced, and this is practically and economically disadvantageous.
To eliminate the above inconveniences, according to the invention, there is provided a water pump which is arranged in a cylinder block of an engine and forms a passage for lubricating oil around a water pump casing which is covered. A water drain hole portion is formed around the water pump casing, a water pump bearing is provided on the inside of the water pump casing, and an inner chamber of the water pump is extended to a position at which it surrounds at least parts of the water pump bearing and the water drain hole portion so as to reduce the thermal influence of the lubricating oil on the water pump bearing or water drain hole portion.
There is also provided a water pump which is arranged in a cylinder block of an engine and forms a passage for lubricating oil around a water pump casing which is covered, wherein a water drain hole portion is formed around the water pump casing, a water pump bearing is provided on the inside of the water pump casing, an inner chamber of the water pump is extended to a position at which it surrounds at least parts of the water pump bearing and the water drain hole portions so as to reduce thermal influence of the lubricating oil on the water pump bearing or water drain hole portion, and ribs for reinforcement are provided in the inner chamber of the water pump casing.
There is also provided a water pump which is arranged in a cylinder block of a V-type engine such that first and second cylinder heads are installed in the cylinder block and first and second cylinder banks are arranged in a V-shape and forms a passage for lubricating oil around a water pump casing which is covered, wherein a water drain hole portion is provided for the water pump casing, a water pump bearing is provided on the inside of the water pump casing, and an inner chamber of the water pump is extended to a position such that it radially surrounds at least parts of the water pump bearing and the water drain hole portion so as to reduce thermal influence of the lubricating oil on the water pump bearing and the water drain hole portion.
There is further provided a water pump which is arranged in a cylinder block of a V-type engine such that first and second cylinder heads are installed in the cylinder block and first and second cylinder banks are arranged in a V-shape and forms a passage for lubricating oil around a water pump casing which is covered, wherein a water drain hole portion is provided for the water pump casing, a water pump bearing is provided on the inside of the water pump casing, an inner chamber of the water pump is extended to a position such that it radially surrounds at least parts of the water pump bearing and the water drain hole portion so as to reduce thermal influence of the lubricating oil on the water pump bearing and the water drain hole portion, and ribs for reinforcement are provided in the inner chamber of the water pump casing.
According to the invention as mentioned above, the inner chamber of the water pump extends up to a position such that it surrounds at least parts of the water pump bearing and the water drain hole portion to reduce the thermal influence by the lubricating oil on the water pump bearing and the water drain hole portion. The ribs for reinforcement are provided in the inner chamber of the water pump casing, hereby improving the rigidity of the casing.